Steel alloy



Patented Apr. 7, 1953 STEEL ALLOY Robert L. Baldwin, Bridgeport, Conn,assignor to The Stanley Works, New Britain, Oonn., a corporation ofConnecticut No Drawing. Application January 30, 1951, Serial. No.208,666

4 Claims.

Thisinvention relates generally to steel alloys and has particularrelation to steel alloys for use in cutlery; such as band saws andknives and especially for use in razor blades. The present, applicationis a continuation-in-part of my copending application's. N. 171,564,filed June 30, 1950, now abandoned, for Steel Alloy.

In the manufacture of cutlery, particularly razor blades, it is desiredto utilize a steel which can be. honed and otherwise treated to producea sharp edge and which will retain this edge in use over long periods oftime.

It is an object of the present invention to' provide a steelalloy forthis purpose which can be utilized toproduce an edge which, is sharperthan that previously considered possible, or con- In the priormanufacture of cutlery, particu larly razor blades, it has been foundgenerally that an improvement in one or more of the many desirablecharacteristics of the steel alloy results in degradation of one or moreof the other de sirable characteristics. Accordingly, it is a furtherobject of the present invention to provide a novel steel alloy whichwill have a high tensile strength without resulting in an undesirabledecrease in ductility. Anotherobject is to provide such a steel alloywhich will have a greater permissible range of hardness without loweringits good cutlery characteristics. Still another object is to, providesuch a steel alloy which will have high hardness characteristics withoutresulting in undesirable brittleness. Still another object is to providesuch a steel alloy which will have substantially all the desiredcharacteristics, ii

eluding fine grain,'low brittleness, high work} ability, high hardness,highhonability and grindability, high cutting ability. and the. desiredtensile strength,elastic limit and elongation.

A still further object of the invention is to provide such a steel alloywhich will have the aforementioned characteristics when used in the formof razor blades reduced in final thickness by as much as 50% less (.003inch) than the thickness of conventional double edge blades (.006 inch).Still another object is to provide such an alloy steel which will havethe aforementioned characteristics and yet will retain its flexibilityand low brittleness so as to permit being tightly wound in the form of acoil without breakage.

A further object of the invention is to provide such an alloy steelwhich will retain the aforementioned characteristics and yet be capableof undergoing long annealing periods of about to, hours in themanufacture of razor blades.

A still further object of the invention is to provide such a steel alloywhich will permit welding of the free end with air cooling when in theform of a band saw strip.

These and other objects of the present invention will be betterunderstood by reference to ventional amounts used in razor blade steelsfor the. following description. I

The present invention resides in the discovery that a surprisinglysuperior. steel alloy for cutlery purposes, and particularly for use inrazor blades and band saws, can be obtained by forming a steelalloyhaving the following composition:

' Per cent Carbon from 1.35 to 1.50 Chromium from .70 tol.00 Vanadium"from" .30 to .45 Silicon from .20 to .50 Manganese from .25 to A0Phosphorus .020 max. Sulphur .020 max.

And the remainder iron and incidental impurities.

The amounts of phosphorus and sulphurpresent are specified above merelyfor completeness, it being apparent that the amounts of these elemeritsnormally are present in the ranges set forth in most steels asincidental impurities. The combined totalamount ofthese latter elements,in general, will be well under one per, cent.

I The manganese component is present. in conthe conventional purposesasa cleanser and deoxidizer and to counteract the harmful effects 3 ofthe sulphur. It has been found that small amounts of manganese in therange of 0.15 to 0.30 per cent are satisfactory in the present alloy forthe manufacture of band saws.

Chromium is generally used in amounts of about 0.15 to 0.25% inconventional razor blade steels which have a carbon content of about1.20 to 1.30 per cent, although higher chromium ranges of the order of0.40 to 0.50 per cent have been used. However, it is known that furtherincreases in the chromium content would cause such blades to be moredifiicult to grind and hone. The specified chromium content primarilyimproves the hardness of the present alloy. Additionally, chromiumpartially dissolves in the iron and partially forms carbides, therebytending to give the increased hardness desired for better i wearresistance while at the same time retaining the desired toughness.Hardness of chromium steels is due to the formation of chromium carbidesor chromium-iron carbides which are intensely hard. For band saw use, ithas been found more satisfactory to stay in the lower limit of thechromium content since this results in better welding characteristics,especially with air cooling. Thus, for band saw steel alloys, a chromiumcontent as low as 0.60-0.80 per cent is preferred. Although this reducedpercentage does lower the hardness to some extent, this is more thanoffset by the improved welding characteristics obtainable.

Vanadium is generally not used in conventional razor blade steels. Inthe present alloy, it has been observed that the vanadium in about thestated range intensifies the eifect of the chromium and tends to keepdown the grain size; that is, it promotes fine grain formation.Moreover, it has been found that the combination of chromium andvanadium increases strength and hardenability while retaining toughnessand fine grain. The specified vanadium content has also been found tominimize the danger of brittleness and tends to retard graphitizing,especially in the manufacture of razor blades involving long anneals ofthe order of 25 to 30 hours where the carbon may revert to graphiteduring a succession of two or three anneals. The vanadium contentspecified has also been found to promote the formation of carbides. Thevanadium content may be somewhat increased, say up to 0.50 per centwithout adverse effect on the alloy characteristics. However, it is oneof the most expensive components and is therefore generally used in theminimum effective amounts.

Silicon is normally considered as a deoxidizer and it is common practiceto add incidental amounts in an alloy steel which is to be heat treated.Also, the addition of the specified amounts of silicon is believed toincrease the tensile strength without resulting in a material decreasein ductility. It appears that the silicon dissolves in the ferrite. Theaddition of the specified percentages of silicon is believed to be inpart responsible for the increases in hardness which have been obtainedwith the present high carbon steel. I have also found, contrary toexpectations, that the high silicon content in the combination of thepresent alloy did not increase the brittleness after hardening andfurthermore did not result in-the formation of graphite after longanneals. I v

The carbon content of conventional razor blade steels generally is 1.20to 1.30 per cent and is generally 1.20 to 1.35 per cent for band sawsteels.

It will be apparent that the steel alloy of. the

present invention utilizes a comparatively high carbon content whichwould be expected to reduce the workability of a steel alloy and make itdifiicult to roll. However, the present alloy is unusual in this respectin that it has been found to be at least as or more workable than asimilar alloy with a lower carbon content of the order of 1.20 to 1.30per cent. It is believed that the combination of the specified amountsof chromium, vanadium, and silicon contents in the present alloyunexpectedly results in improved workability for the higher carbonsteel. It is also believed that the higher carbon in combination withthe specified chromium, vanadium and silicon results in a bettercombination of hardness, resistance to abrasion, and the ability to holda keen edge together with unusual combinations of toughness and cuttingability.

The present invention is characterized in the provision of relativelylow chromium content and a comparatively high ratio of carbon tochromium and a comparatively low ratio of chromium to silicon in a highcarbon steel having a relatively high silicon content. Thus, the presentinvention is characterized in the provision of the specified additionsof alloys in the form of silicon, chromium, and vanadium to anexceptionally high carbon steel resulting in a desirable increase instrength, hardness and wear-resistance without serious loss in ductilityand at the same time avoiding undue brittleness after heat-treatment oftheir stock such as used for razor blades or band saws.

The steel alloy of the present invention can be made in accordance withthe conventional practice for forming a multiple steel alloy such as,for example, by blending the elements in an electric furnace or in anopen hearth furnace, the various elements being added either to the bathor in the ladle.

When the alloy of the present invention is produced in any desiredmanner and containing the elements mentioned in the range specified, itmay be hot and cold rolled to the form desired for use in cutleryproducts. In the manufacture of conventional razor blades, for example,it is customary to hot roll the steel in ribbon form to a thickness ofapproximately .066" and to cold roll the strip thereafter to a finalthickness de-' sired, generally of the order of .006". The steel may beannealed'between cold rollings in the usual manner to relieve stresses.

After rolling, the steel alloy of thepresent invention preferably ishardened and tempered following conventional practices to obtain thedesired final mechanical properties. It is an advantage of the steelalloy of the present invention, however, that a greater range ofhardness may be attained without loss of toughness or resistance toabrasion and without acquiring brittleness. As a result, the steel alloyof the invention can be made harder than steels and steel alloysheretofore used for cutlery purposes and at the same time, the finalproduct can be honed to a keener edge, there being no difficulty inaccordance with the present invention after hardening and temperingshows that .there is formed a large amount of carbides precipitatedAlso, the resulting keen edge will not be,

(5 :in ithe:formof'veryifina: uniformly divided :spheroids. Thisstructure is ,beneficialior obtaining the good cutting edge and wearresistance referred to above.

The following examples are illustrativeqof the --present.stee1 .alloy: r

7 Percent Carbon Approximately 1.38 Chromium Approximately 0.89 VanadiumApproximately 0.38 Silicon Approximately 0.50' Manganese Approximately0.32

EXAMPLE 2 Per cent Carbon Approximately 1.38 Chromium Approximately 1.00Vanadium .Approximately 0.43 Silicon Approximately 0.21 Manganese 1Approximately 0.26

'This steel alloy was hot rolled and batch annealed at 0.066 thickness;then rolled to 0.050 thickness and batch annealed; then rolled to 0.037thickness and continuously annealed.

A conventional steel alloy for razorblade production having thefollowing analysis was similarly treated:

Conventional steel alloy Carbon Approximately 1.25 per cent ChromiumApproximately 0.20 per cent Manganese Approximately 0.35 per centSilicon Approximately 0.20 max. Phosphorous Approximately 0.020 max.Sulfur Approximately 0.020 max.

Remainder iron with incidental impurities.

Comparative tests gave the following results:

Alloy of Conven- Example 2 tional Elastic Limit L 85,000 64, 500 Tensilestrength 97, 000 84, 400 Percent elongation at 2 inches 12 Rockwellhardness B 96/97 13 89 Tensile strength of finished strip 06"). 138, 000129,000 T Rockwell hardness.. 85.5. 83. 5

In the form of band saws 0.750 inch wide and .0320 inch thick(conventional steel alloy) and 0.030 thick (Example 2), cutting testswere run on a regulation test bar. The conventional steel alloy went outof line at cuts and failed completely at 48 cuts. The alloy steel ofExample 2 failed at 53 cuts, all of which were straight.

EXAMPLE 3 Per cent Carbon Approximately 1.35 Chromium Approximately 0.80Vanadium Approximately 0.32 Silicon Approximately 0.27 ManganeseApproximately 0.32

Remainder iron and incidental impurities.

"6 "This steel alloy and theconventionatsteel 'alloy set forth abovewere treated and tested as follows:

- Conventional -(e) The steel otExample 3-after batclra 5 (a) Hot rolledand one long'batch anneal at Ainchesby 0.066 inch:

Elastic limit Tensile strength Percent elongation in. 111 Rockwellhardness (b) Thesame steels were put through'a con-' tinuous anneal andtested:

Elastic limit Tensile strength Percent elongation 1 Rockwell hardness(c) The same steels after 'batch anneal at; 0.066" were .cold rolled to0.050 inchand given a second batch anneal-and testedr- Elastic limit.593.1600; Tensile strength. Percent elongatio Rockwell hardness (d) Thesame steels after batch anneal at 0.066 were cold rolled to 0.050 andannealed continuously and tested:

Percent elongation in 2 inches..

Rockwell hardness neal at .066 and continuous-anneal at .050

was cold rolled .to .037 and annealed continuously and tested:Elastic'limit Tensile strength. Percent elongation 1 nches Rockwellhardness Practical shaving tests were conducted with 203 adult men withone double edge razor blade each, made of the steel alloy of Example 1.The results of the survey were as follows:

Reported excellent 20 Reported unusually good 2 Reported very good .142Reported fine 1 Reported good 28 Requested new blades forfurther trial.5 Reported poor 4 In all cases (4) where the blade'was reported poorand where a. new blade was requested for further trial (5), the'newblade'was'reported as very good.

In a further practical shaving test, 36 men using 4 double edge bladeseach :on stubble of at least 36 hours growthyan average of'10.5 verygood shaves per'p'erson penblade was found.

EXAMPLE 4 .:Per cent Carbon Approximately 1.41 Chromium Approximately0.88 Vanadium Approximately 0.36 Silicon .Approximately 0.51 ManganeseApproximately0.3-3

Treatment and testresults were generally similar to those of the steelalloy of Example 1, with the following general variations:

Tensile strength of finished strip 138,500

(.881 X .006). r 30 T Rockwell hardness 85.5

EXAMPLE 5 Per cent Carbon Approximately 1.36 Chromium Approximately 0.90Vanadium Approximately 0.40 Silicon Approximately 0.49 ManganeseApproximately 0.32 Remainder iron and incidental impurities.

This steel alloy was treated and tested generally similar to Example 1with the following general variations:

Tensile strength of finished strip 135,000

. (.881 x .065"). 30 T Rockwell hardness 84.5

EXAMPLE 6 Per cent Carbon Approximately 1.48 Chromium Approximately 0.70Vanadium Approximately 0.32 Silicon Approximately 0.21 ManganeseApproximately 0.37

Remainder iron and incidental impurities.

This steel alloy when treated like Example 2 will test about the samewith the exception that the hardness will be reduced to about B 94/95.This alloy when used in the production of a band saw as in Example 2 maybe readily welded with air cooling.

Razor blade strips made in accordance with the present invention, whenhardened, tempered and honed by conventional methods, result in anunexpected improvement in the sharpness which can be produced, whichrenders the blade greatly superior to those now commercially available.As a result of the improved structure of the metal as well as itstoughness and other properties, the edge is not destroyed by honing to ahigh degree of sharpness and the edge has a remarkable resistance toabrasion or crumbling or other dulling effects.

One of the primary features of the present alloy is that it has agreater permissible range of hardness while retaining its good cuttingcharacteristics. Another primary feature is that the present alloyenables the use of a higher hardness while avoiding brittleness. Forexample, one of the best conventional razor blade steels has a 30 Nscale of Rockwell hardness of about 7 9. With this conventional razorblade steel, hardness variations slightly below '79 result in aninferior shave, whereasvariations slightly above 79 result inunacceptable brittleness. With the present alloy. greater variations arepermissible without adverse effect on the overall characteristics of therazor blades.

The various characteristics referred to throughout the specificationvary in importance depend- While the Carbon 1.35 to 1.50 Chromium 0.70to 1.00 Vanadium 0.30 to 0.45 Silicon 0.20 to 0.50

Remainder iron and incidental impurities.

2. A razor blade comprising an alloy steel having the following elementsin the approximate percentage ranges:

Carbon 1.35 to 1.50 Chromium 0.70 to 1.00 Vanadium 0.30 to 0.45 Silicon0.20 to 0.50 Manganese 0.25 to 0.40

Remainder iron and incidental impurities.

3. A razor blade comprising an alloy steel having the following elementsin the approximate percentage ranges:

Carbon 1.35 to 1.50 Chromium 0.70 to 1.00 Vanadium 0.30 to 0.45 Silicon0.20 to 0.50 Manganese 0.25 to 0.40 Phosphorous 0.020 maximum Sulfur0.020 maximum Remainder iron and incidental impurities.

A razor blade comprising an alloy steel having the following elements inthe approximate percentage proportions:

Carbon 1.38 Chromium 0.89 Vanadium 0.38 Silicon 0.50 Manganese 0.32

Remainder iron and incidental impurities.

ROBERT L. BALDWIN.

REFERENCES CITED The following references are of record in the file ofthis patent:

FOREIGN PATENTS Country Date Great Britain June 10, 1920 OTHERREFERENCES Vanadium Steels and Irons, pages and 122. Published by theVanadium Corp. of America. Received at the U. S. Patent Ofiice January4, 1937.

Number

1. A RAZOR BLADE COMPRISING AN ALLOY STEEL HAVING THE FOLLOWING ELEMENTSIN THE APPROXIMATE PERCENTAGE RANGES: